As an image forming apparatus that forms color and monochrome images, there is known, for example, an image forming apparatus that includes laser units, photoconductive drums, and developing devices corresponding to respective color components of Y (yellow), M (magenta), C (cyan), and B (black), a transfer device, and a fixing device and can perform image formation in monochrome and image formation in color. Light sources, reflection mirrors, slit glasses, and the like corresponding to the respective colors are provided in the laser units.
In the image forming apparatus of this type, for example, as disclosed in JP-A-2005-192076 (laid open on Jul. 14, 2005), there is known an image forming apparatus in which shutters are provided on a photoconductive drum side of slit glasses to adjust a blocking state. In the image forming apparatus, the shutters in which plural blocking sections and plural transmitting sections corresponding to respective colors are formed are moved in a direction crossing beams to adjust a blocking state of the beams.
In general, the blocking state is adjusted according to switching of two states; an open state in which beams corresponding to all the colors are transmitted in association with the respective plural transmitting sections and a closed state in which the beams corresponding to all the colors are blocked in association with the respective plural transmitting sections.
However, in the image forming apparatus having the configuration described above, the slits corresponding to all the colors are in the open state even during monochrome printing. The slits corresponding to the colors other than black for which beams are not emitted during the monochrome printing are opened. Therefore, since unnecessary sections are opened, toners, dust, and the like tend to adhere to the sections. As a result, an image failure is caused.
Therefore, it is an object of the present invention to prevent adhesion of toners, dust, and the like and prevent an image failure.